1. Technical Field
Various embodiments of the present disclosure relate to semiconductor technologies and, more particularly, to an apparatus and method for removing particles present on a wafer using photoelectrons and an electric field.
2. Related Art
Semiconductor technologies may include processes for forming patterns on a substrate or a wafer to integrate electronic circuits. Contaminants such as particles present on or adsorbed onto a surface of the wafer may cause process failures. Thus, the particles adsorbed onto the surface of the wafer have to be removed in order to form uniform patterns having desired features throughout the wafer.
Particles present on or adsorbed onto a wafer may cause process defects, and thus a process yield may be reduced. Accordingly, technologies for removing particles present on or adsorbed onto a wafer become more important. In particular, if particles are adsorbed onto a back-side surface of a wafer, a front-side surface of the wafer may be sloped when the wafer is loaded onto a chuck of a wafer processing apparatus. In such a case, process conditions on the front-side surface of the wafer may be different according to locations on the wafer. For example, if a patterning process is performed on a material layer that is formed on the front-side surface of the wafer whose back-side surface is contaminated with particles, non-uniform patterns may be formed on the front-side surface of the wafer because of a sloped profile of the front-side surface of the wafer due to the particles.
In an exposure step of a lithography process for transferring mask patterns of a photo mask onto a wafer, a front-side surface of the wafer loaded onto a wafer stage of exposure equipment may exhibit a sloped profile when particles exist on a back-side surface of the wafer, such that a depth of focus (DOF) may be different according to locations on the wafer. This may cause a defocus phenomenon. The defocus phenomenon may lead to a non-uniform exposure step. As a result, the uniformity of patterns formed on the front-side surface of the wafer may be degraded. Accordingly, a lot of effort has been introduced to remove particles adsorbed onto a back-side surface of a wafer prior to performing a wafer-processing process, such as an exposure step of a lithography process.